Developing solution for lithographic printing plate precursor and method for making lithographic printing plate

Abstract

An alkaline developing solution for development of a presensitized plate for use in making a lithographic printing plate, which developing solution comprises a polyoxyalkylene adduct of alkylene diamine, a polyoxyalkylene compound having an acid radical, and an anionic surfactant; a method for making a lithographic printing plate comprising the steps of: light-exposing a presensitized plate for use in making a lithographic printing plate; and developing the light-exposed plate with an alkaline developing solution comprising a polyoxyalkylene adduct of alkylene diamine, a polyoxyalkylene compound having an acid radical, and an anionic surfactant.

Description

FIELD OF THE INVENTION [0001] The present invention relates to an alkaline developing solution for use in processing a lithographic printing plate precursor, i.e., a presensitized plate for use in making a lithographic printing plate (hereinafter possibly referred to as “PS plate”), and further a method for making a lithographic printing plate using the alkaline developing solution. More particularly, the present invention relates to an alkaline developing solution which is suitable for making a lithographic printing plate from a PS plate capable of achieving direct plate making, that is, making a printing plate directly by exposing the PS plate to infrared laser scanning based on digital signals from computers or the like, and a method for making a lithographic printing plate using said alkaline developing solution. BACKGROUND OF THE INVENTION [0002] There have been great strides made in the study of laser in recent years. In particular, solid lasers and semiconductor lasers that c...

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Benefits of technology

[0017] According to the alkaline developing solution of the present invention, a highly sharp and clear image can be formed in a printing plate without damages to the formed image areas. The alkaline developing solution of the present invention can exhibit a certain performance and retain favorable image forming performance, even if components of an image recording layer dissolve into the developing solution in course of processing. Further, according to the alkaline developing solution of the present invention, occurrence of development sludge originated from the component of an image recording layer can be suppressed. Accordingly, a method for makin

Problems solved by technology

However, in the above lithographic printing plate precursor of positive-working mode for infrared laser scanning, there is a problem that it is difficult to make highly sharp and clear images, because a difference of dissolving rate in an alkaline developing solution between a light-exposed portion and an unexposed portion is small.

Furthermore, in a heat-sensitive printing plate precursor as described above, there is a problem that excessive development or defective development tends to take place depending on variation of use conditions, since a difference between a resistance of dissolution residing in an unexposed portion (image portion) to a developing solution and a solubility of a light-exposed portion (non-image portion) in a developing solution is still insufficient in various use conditions.

In addition, the image-forming ability of the lithographic printing plate precursor depends on a heat generation on the surface of an image recording layer through an infrared laser exposure, and in the vicinity of a substrate, quantity of heat which is used for dissolution of the image recording layer, i.e., for an image formation is small due to a dispersion of heat, resulting in that a difference between light-exposure and unexposure becomes small and a reproducibility of highlight becomes insufficient.

Such insoluble matter becomes sludge in a processin

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